1. Field of the Invention
This invention relates to a process for producing glycerides using an enzyme. More particularly, the present invention relates to a process for synthesizing glycerides by reacting a fatty acid or a fatty acid ester with glycerol in the presence of a lipase, wherein, as the lipase, a monoglyceride lipase and/or a diglyceride lipase is used to produce glycerides containing little or no triglyceride and consisting substantially of a monoglyceride and a diglyceride. Most preferably, the present invention relates to a process for synthesizing glycerides by reacting a fatty acid or a fatty acid ester with glycerol in the presence of a lipase, wherein the above mentioned lipase is used to produce glycerides completely or substantially free from triglyceride and diglyceride and consisting substantially of a monoglyceride. Monoglycerides and diglycerides are useful as emulsifiers and antimicrobial agents.
2. Description of the Prior Art
Lipases are enzymes which hydrolyze fats and oils and esters of fatty acids. However, it is known that, under certain conditions, lipases cause an esterification reaction which is the reverse of hydrolysis and thereby glycerides or esters can be synthesized from a fatty acid and glycerol or from a fatty acid and an alcohol (J. Gen. Appl. Microbiol., 10, 13-22, 1964; Proc. IV IFS: Ferment. Technol. Today, 315-320, 1972, issued by Society of Fermentation Technology Japan; Biochim. Biophys. Acta, 489, 415-422, 1977; Bull. Tech/Gattefosse Rep., 76, 34-36, 1983; J. Am. Oil Chem. Soc., 61, 191-195, 1984; Japanese Patent Publication No. 7754/1976, Japanese Patent Publication No. 23535/1982, Japanese Patent Laid-Open No. 118094/1984, Japanese Patnet Laid-Open No. 118095/1984, etc.). The lipases used in this prior art and the most popular lipases are so-called triacylglycerol lipases which are also called triglyceride lipases. These lipases have a specificity not only to triglycerides but also to diglycerides and monoglycerides, although the specificities each glyceride are different. Glycerides synthesized by the esterification reaction using the action of these triglyceride lipases are usually a mixture of a triglyceride, a diglyceride, and a monoglyceride and, even when these glycerides consist substantially of a monoglyceride and a diglyceride, the content of monoglyceride in the glyceride mixture is low.
Monoglycerides and diglycerides are in wide use as emulsifiers for foods, cosmetics, medicines, etc. It is known that, in the ability to act as an emulsifier, monoglycerides are far superior to diglycerides and the presence of triglycerides is not desirable. Particular types of monoglycerides such as monolaurin, monocaprin and the like are in use as antimicrobial agents or an antiseptic agents, e.g. for foods. In general, glycerides used as emulsifiers are required to contain at least about 90 mole % of monoglycerides. Hence, in the conventional production of such glycerides, it has been necessary to subject a glyceride mixture to molecular distillation or the like to enhance the content of monoglycerides.